1. Field of the Invention
This invention relates to methods and apparatus for separating and removing sand from fluid streams, and more particularly, but not by way of limitation, to fluid stream sand separation and removal methods and apparatus which utilize one or more sand filters for facilitating sand separation.
2. Setting of the Invention
Fluid streams produced by oil and gas wells often contain subterranean formation sand which can range in size from fine to relatively coarse particles. If not removed, the sand causes the rapid erosion of metal surfaces contacted by the fluid stream such as tubular goods, valves and vessel internals.
Various methods and apparatus which utilize filter means for separating sand from fluid streams have been developed and used heretofore. Such methods and apparatus generally involve the use of one or more removable filters disposed within a separator vessel arranged whereby the fluid stream containing sand is caused to slow down and change direction in a first compartment in the vessel and then flow from the first compartment through the filters into a second compartment from where the filtered fluid stream is withdrawn. The combination of changing the direction of flow slowing the velocity and filtering the fluid stream causes sand to be separated therefrom and to be accumulated in the first compartment. In order to remove the sand from the first compartment in the vessel, a sand wash liquid, most commonly water, is periodically introduced into the first compartment while simultaneously withdrawing sand and wash liquid therefrom by way of one or more outlet connections attached thereto.
The introduction of the wash liquid has heretofore been accomplished by discharging it from one or more slotted or perforated wash pipes disposed in the lower portion of the first compartment of the separator vessel. A problem encountered in the use of such sand separators is that sand often finds its way into the slotted or perforated wash pipe whereby the pipe becomes clogged and the introduction of wash liquid into the separator prevented. This in turn requires that the separator be shut down and opened so that sand in the separator and wash pipe can be manually removed therefrom.
Another problem experienced with prior sand separators utilizing sand wash removal systems is that the sand outlet connections and shut-off valves connected thereto often become clogged with sand. As the sand settles in the bottom of the separator vessel, it packs into the sand outlet connections. The wash liquid discharged in the separator vessel often cannot fluidize such packed sand in the connections whereby the accumulated sand and wash liquid cannot be efficiently removed, again requiring that the separator be shut down and cleaned out. Occasionally, even where the sand outlet connections are not plugged, the shut-off valves connected to the outlet connections bridge over with sand whereby sand and wash liquid removal is prevented.
There is a need for a fluid stream sand separation and removal method and apparatus which utilize filter means for final sand separation and wash liquid for sand removal wherein wash pipe, sand outlet connection and shut-off valve clogging is substantially prevented.